Oxypoda alternans (Gravenhorst, 1802)
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POLYPHAGA Emery, 1886
STAPHYLINOIDEA Latreille, 1802
OXYPODINI Thomson, C.G., 1859
Oxypoda Mannerheim, 1830
This is a widespread and generally common western Palaearctic species occurring from lowlands to the alpine zone from Europe through Asia Minor to Afghanistan, India and the western Himalayas. In Europe it is common in suitable habitats more or less everywhere, reaching north into the UK and to the Arctic Circle in Scandinavia. Here it is common throughout southern and central England and Wales, rather less so in northern England and very local and sporadic in Scotland, including the Western isles, and in Northern Ireland. Adults are present year-round, they overwinter among decaying fungi or infested wood and are active over a long season from early spring until late in the autumn, peaking in abundance during spring/early summer and, especially, in the autumn when they may be very abundant among decaying sporocarps. Typical habitats are open woodland and wooded parkland with plenty of trees in various stages of decay but, especially during late summer and autumn, adults may appear at fungi on trees in hedgerows or gardens etc. Both adults and larvae are thought to be mycophagous (although this has been questioned) and larvae probably develop through the summer as large populations of adults often appear in late summer and autumn. A wide range of fungi have been recorded hosting the species including Cerioporus squamosus (Huds.) Quélet, Inonotus dryophilus (Berk.) Murrill, I. rheades (Pers.) P. Karst., I. radiatus (Sowerby) P. Karst., Climacocystis borealis (Fr.) Kotl. & Pouzar (1958), Laetiporus sulphureus (Bull.:Fr.) Murrill, Piptoporus betulinus (Bull.) P. Karst. and species of Collybia (Fr.) Staude, and Lactarius (Fr.) S.F. Gray. Adults are crepuscular and nocturnal but are easily sampled during the day by tapping sporocarps over a net or sheet, they usually occur in numbers and usually among many other small staphs although their distinctive colour (there are other coloured species) generally makes them obvious to the experienced eye. During the day they generally hide in spore tubes or among gills but, especially during the autumn and winter, they may be found in numbers among layers of large decaying sporocarps in contact with the ground.
3.2-3.8 mm. Dorsal surface with fine silky pubescence, colour varies but typically with the head dark (often black), pronotum, elytra and abdomen pale brown or reddish-brown, elytra darkened about the scutellum and hind angles (this may be extensive), and abdomen with a transverse dark band towards the apex and sometimes with various basal segments darkened medially. Antennae dark with two or three basal segments and sometimes the terminal segment pale. Head large, prognathous, with large, flat eyes and long, rounded and finely bordered temples, surface evenly convex and very finely punctured. Maxillary palps slender, the penultimate segment expanded, longer than the basal antennomere and the terminal segment diminutive. Antennae inserted dorsally about the outer margin of the mandibles and about as long as the head and pronotum combined, segment 3 as long as or, usually, slightly shorter than segment 2 and segments 7-10 distinctly transverse. Lateral margins of the pronotum and elytra without long erect setae. Pronotum transverse, about 1.25X wider than long, broadest near obtuse posterior angles and narrowed to a rounded apical margin, surface evenly convex and without sculpture, very finely and closely punctured (X50). Elytra distinctly broader than the pronotum and slightly dilated from rounded shoulders to a strongly sinuate apical margin, this giving the effect of protruding posterior angles, surface without striae and punctured as the pronotum. Abdomen gently and gradually tapering, basal segments bordered laterally and impressed across the base, all segments very finely punctured (X50) and with dense silky pubescence. Legs long and slender, femora unarmed and tibiae without erect setae. Tarsi 5-segmented, the basal segment of the hind tarsi at least as long as the terminal segment.